Skip hover state updates during node drag to prevent re-renders

When dragging a node over another, onMouseEnter/onMouseLeave were
firing on underlying nodes, updating hoveredNodeId in Zustand and
triggering re-renders of nodes with large base64 images.

- Add isDraggingNodeRef (set on onNodeDragStart, cleared on
  onNodeDragStop) to suppress hover events during drag
- Add CSS contain: layout style paint on BaseNode content area to
  isolate repaints within each node

https://claude.ai/code/session_01MvD1n4QeXutgwUpKJuDGHa

src/components/WorkflowCanvas.tsx

@@ -268,6 +268,8 @@ const findScrollableAncestor = (target: HTMLElement, deltaX: number, deltaY: num
 
 /** Shared ref so child components (BaseNode) can check panning state without re-rendering */
 export const isPanningRef = { current: false };
+/** Shared ref so child components (BaseNode) can skip hover updates during node drags */
+export const isDraggingNodeRef = { current: false };
 
 export function WorkflowCanvas() {
   const { nodes, edges, groups, isModalOpen, showQuickstart, navigationTarget, canvasNavigationSettings, dimmedNodeIds } =
@@ -1964,7 +1966,8 @@ export function WorkflowCanvas() {
         onConnectEnd={handleConnectEnd}
         onMoveStart={() => { isPanningRef.current = true; setHoveredNodeId(null); }}
         onMoveEnd={() => { isPanningRef.current = false; }}
-        onNodeDragStop={handleNodeDragStop}
+        onNodeDragStart={() => { isDraggingNodeRef.current = true; }}
+        onNodeDragStop={(event, node) => { isDraggingNodeRef.current = false; handleNodeDragStop(event, node); }}
         onSelectionChange={handleSelectionChange}
         nodeTypes={nodeTypes}
         edgeTypes={edgeTypes}

src/components/nodes/BaseNode.tsx

@@ -3,7 +3,7 @@
 import { ReactNode, useCallback, useRef, useLayoutEffect } from "react";
 import { Node, NodeResizer, OnResize, useReactFlow } from "@xyflow/react";
 import { useWorkflowStore } from "@/store/workflowStore";
-import { isPanningRef } from "@/components/WorkflowCanvas";
+import { isPanningRef, isDraggingNodeRef } from "@/components/WorkflowCanvas";
 import { getMediaDimensions, calculateAspectFitSize } from "@/utils/nodeDimensions";
 
 const DEFAULT_NODE_DIMENSION = 300;
@@ -297,15 +297,15 @@ export function BaseNode({
           ${className}
         `}
         onMouseEnter={() => {
-          if (isPanningRef.current) return;
+          if (isPanningRef.current || isDraggingNodeRef.current) return;
           setHoveredNodeId(id);
         }}
         onMouseLeave={() => {
-          if (isPanningRef.current) return;
+          if (isPanningRef.current || isDraggingNodeRef.current) return;
           setHoveredNodeId(null);
         }}
       >
-        <div ref={contentRef} className={contentClassName ?? (fullBleed ? "flex-1 min-h-0 relative" : "px-3 pb-4 flex-1 min-h-0 overflow-hidden flex flex-col")}>{children}</div>
+        <div ref={contentRef} style={{ contain: "layout style paint" }} className={contentClassName ?? (fullBleed ? "flex-1 min-h-0 relative" : "px-3 pb-4 flex-1 min-h-0 overflow-hidden flex flex-col")}>{children}</div>
       </div>
       {settingsPanel && (
         <div ref={settingsPanelRef}>